Hydroxyalkyl polygalactomannans by reaction with certain halo fatty acid compounds

ABSTRACT

The hydration rate of hydroxyalkyl polygalactomannans is improved by reaction with certain halo fatty acids or the alkali metal salts thereof. Such products find utility as thickeners for various fluids.

United States Patent Nordgren et a1.

[ 1 Mar. 27, 1973 HYDROXYALKYL POLYGALACTOMANNANS BY REACTION WITHCERTAIN HALO FATTY ACID COMPOUNDS Inventors: Robert Nordgren; Duane A.Jones;

Harold A. Wittcoff, all of Minneapolis, Minn.

Assignee: General Mills Chemicals, Inc.

Filed: May 26, 1970 Appl. No.: 40,744

US. Cl. ..260/209 R, 99/144, 252/8.55 R,

252/316, 424/49, 424/70 Int. Cl ..C07c 47/18 Field of Search ..260/209R, 234 R Primary Examiner-Lewis Gotts Assistant Examiner-1ohnnie R.Brown Attorney-Anthony A. Juettner and Gene 0. Enockson [57] ABSTRACTThe hydration rate of hydroxyalkyl polygalactomannans is improved byreaction with certain halo fatty acids or the alkali metal saltsthereof. Such products find utility as thickeners for various fluids.

2 Claims, No Drawings I-IYDROXYALKYL POLYGALACTOMANNANS BY REACTION WITHCERTAIN HALO FATTY ACID COMPOUNDS This invention relates to a processfor preparing hydroxyalkyl polygalactomannan derivatives having improvedproperties and to the resulting products. More particularly, it relatesto such a process wherein halo fatty acids or the alkali metal saltsthereof are used to increase the hydration rate of the hydroxyalkylpolygalactomannans.

Hydroxyalkyl ethers of polygalactomannans, and especially guar gum, havebeen made by the reaction of the. polygalactomannans with an alkyleneoxide which has at least 3 carbon atoms. The alkylene oxide having atleast 3 carbon atoms reacts with hydroxyl groups present in thepolygalactomannan. The resulting products have a degree of substitution(D.S.) of from about 0.05 to and preferably about 0.1 to 4. In guar gum,for example, the basic unit of the polymer is comprised of two mannoseunits with a glycosidic linkage and a galactose unit attached to one ofthe hydroxyls of the mannose units. On the average, each of the sugarunits has three available hydroxyl sites, all of which may react. Inaddition, a new hydroxyl group is added with each alkylene oxide groupand it too can react. Theoretically, then, there is no limit to theamount of alkylene oxide that may be added to the polygalactomannan. Asa practical matter, however, a degree of substitution of about 4 or 5represents the practical upper limit. D.S. products of 0.05 to 5 areachieved by reacting the alkylene oxide with the polygalactomannanemploying from about 0.1 to 6.0 oxirane equivalents from the alkyleneoxide per anhydrohexose unit of the polygalactomannan.

The hydroxyalkyl ethers as above described are prepared from alkyleneoxides having up to 8 carbon atoms. Generally, the oxirane group is aterminal vicinal epoxy group. Such alkylene oxides may be represented bythe following formula:

where R is an alkyl group having from one to six carbon atoms. R ispreferably methyl, such as propylene oxide. R may also, however, beethyl, propyl, butyl, amyl, hexyl and the like.

Basically, the hydroxyalkyl ethers are prepared by the reaction of thepolygalactomannan with the alkylene oxide in the presence of an alkalinecatalyst. Commercially available guar gum generally contains from about8 to percent moisture by weight. For convenience, the reaction willhereinbelow be described with reference to guar gum and propylene oxideto provide the hydroxypropy] ether or polyhydroxypropyl ether of guargum. The rate of reaction is dependent on the catalyst concentration andthe temperature. Temperatures substantially higher than room temperaturewill generally require pressure equipment or solvent reflux. Averagereaction efficiency is in the range of 60 to 80 percent. The reactionmay be illustrated in its simplest, idealized form by the followingequation:

The final product may be more conveniently shown by the formula Thislatter formula more clearly illustrates the attachment of the R group tothe same carbon atom as the hydroxyl group, the hydroxyl group beingattached to a secondary carbon atom. With propylene oxide the R group ismethyl. With other alkylene oxides having a terminal, vicinal epoxidegroup, the R group will be an alkyl group having two carbon atoms lessthan the alkylene group of the alkylene oxide. Guar" in the formularepresents guar minus x number of hydroxyl groups capable of reactingwith the alkylene oxide and x is an integer from 1 to 3 for ananhydrohexose unit of guar.

Formula (2) above represents the idealized formula for such hydroxyalkylether species. As indicated above, each sugar unit contains 3 hydroxylgroups which may react with the alkylene oxide. In such a case, x is aninteger from 1 to 3 in any one sugar unit of the guar gum. Variousdegrees of substitution may be achieved, however. As also indicatedabove, it is possible to have a degree of substitution greater than 3,as the alkylene oxide may also react with the hydroxyl group attached tothe secondary carbon atom of the alkyl group subsequent to the reactionof a molecule of alkylene oxide with one of the reactive hydroxyl groupsof the polygalactomannan. In such event, the hydroxyalkyl ether productmay be illustrated by the formula where x is an integer up to 3 and y isan integer dependent on the degree of substitution, which, as apractical matter, is rarely in excess of 3. It is difficult to specifythe exact integers for x and y in any one specific product and,accordingly, the product is described by reference to the degree ofsubstitution which indicates the amount of alkylene oxide reacted.

In view of their complex nature, it is difficult to define the describedethers by any simple chemical name. The products are most convenientlydefined as a hydroxyalkyl ether of a polygalactomannan in which thealkyl group has three to eight carbon atoms and the hydroxyl group isattached to a secondary carbon atom. In this manner, both the idealizedsimple ethers and the complex products are encompassed. In the idealizedformula (2) above, the product would be monoor poly-2-hydroxy,Z-aIkyIethyl-guar ether in which the alkyl group has from one to sixcarbon atoms. The products may, of course, also be described byreference to the reactants.

Such hydroxyalkyl ethers of polygalactomannans have various uses. Thusthey find use as thickening agents for various fluids, including oilwell fracturing fluids. At a degree of substitution of 0.4 and above,they dissolve in water with extreme foaming. This property makes themuseful as an air entruiner, a toothpaste bodying agent, a thickener forexplosive slurries and a thickener for cream-type hair shampoos. Becauseof the presence of the alkyl group attached to the same carbon atom asthe hydroxyl group, the products have lipophyllic properties and thusutility as an emulsifier-thickener for emulsions such as saladdressings. Products having a D5. in the range of 0.5 to 1.2 provideprogressively clearer solutions free from insolubles which are incontrast to unmodified guar, for example, which gives very cloudysolutions having appreciable insolubles.

In many of the above uses, it would be desirable to increase thehydration rate of the hydroxyalkyl polygalactomannans. We have nowdiscovered that such increased rate of hydration can be obtained by alsoreacting the polygalactomannans with certain halo fatty acids or thealkali metal salts thereof.

The term polygalactomannans as used herein includes the general class ofpolysaccharides containing both galactose and mannose units. Thepolygalactomannans are usually found in the endosperm sections ofleguminous seeds such as guar, locust bean, honey locust, flametree andCassia occidentalis. The invention has particular value in providingimproved derivatives of guar gum due to the ready availability of thesame.

In accordance with the present invention, the hydroxyalkyl derivativesof polygalactomannans are modified by reaction with a halo fatty acid oralkali metal salt thereof. Suitable halo fatty acids includechloroacetic acid, chloropropionic acid, chlorobutyric acid and thelike. The said halo fatty acids can have two to four carbon atoms in thefatty chain. It is preferred to use the sodium salts of the halo fattyacids and sodium chloroacetate is the particularly preferred reactant.

It is preferred to include the halo fatty acid reactant as describedduring the reaction of the polygalactomannan with the described alkyleneoxides. The reaction may be conducted at room temperature or elevatedtemperatures. At room temperature, the reaction is slower. A generaltemperature range would be from about 17C. to about 100C. While highertemperatures might sometimes be used, such as up to 125C, there isgenerally no advantage thereto and higher temperatures may have anadverse effect on color of the product. Where temperatures other thanroom temperature are employed, temperatures on the order of about50-100C. are generally used.

The reaction is carried out using an alkaline catalyst. Such catalystsare in general the alkali metal or alkaline earth metal hydroxides, suchas sodium, potassium or calcium hydroxide. Ammonia may also be used. Nospecial advantage, however, is obtained by the use of more exotic basicor alkaline catalysts over the use of NaOH which is the most commonlyavailable alkaline catalyst. In general, however, it is only necessarythat an alkaline catalyst be present, and the process is not restrictedto the use of any specific catalyst, although NaOl-l is preferred.

Only small amounts of the catalyst need be employed. Thus it isgenerally not necessary to exceed percent by weight of thepolygalactomannamalthough larger amounts might be used. A preferredrange is 0.1 to 5 percent by weight of the polygalactomannan.

The reaction may be conducted at atmospheric pressure, under reflux orat elevated pressures in a closed reactor. The exact pressure is notcritical and the reaction is preferably carried out under refluxconditions. The time of reaction is generally dependent on thetemperature, amount of reactants and the degree of substitution desired.At room temperature long periods of time are required, particularlywhere high degrees of substitution are desired. At higher temperatures,under reflux or under pressure, shorter time periods are employed. Underthe slowest conditions, times up to 100 hours may be required.Generally, at least about three hours are required, although undercertain conditions and low degrees of substitution, shorter time periodsmay be employed. At lower levels of substitutiion at elevatedtemperatures, time periods of from 5 to 15 hours are commonly employed.

The reaction may be conducted in the substantial absence of water orsolvent (no water added) although the efficiency of reaction is very lowwithout the addition of water. Accordingly, the reaction is generallyconducted in the presence of water to provide higher reactionefficiency. In the absence of other solvents, catalytic amounts of wateron the order of about 3 to 8 percent based on the polygalactomannan arepreferably employed, these small amounts generally being employed wherehigher temperatures are used. Where lower temperatures and atmosphericpressure are used, generally larger amounts of water will be employed.Further, it is preferred to utilize organic solvents, eitherwater-miscible or water-immiscible. Illustrative of such organicsolvents are isopropanol (watermiscible) and heptane (water-immiscible).Other unreactive organic solvents may be employed although the twomentioned are preferred. Such other organic solvents are the commonaliphatic hydrocarbons having from 5 to 10 carbon atoms which arecommercially available, such as heptane and hexane. Alkanols higher thanmethanol, those having from 2 to 6 carbon atoms, may also be employed,such as t-butanol. When employed with a solvent, such as isopropanol orheptane, from 10 to 80 percent water based on the weight of thepolygalactomannan is preferably used with from 30 to percent being mostdesirable with the water-miscible solvents and 20-30 percent being mostdesirable with the water-immiscible solvents.

Where organic solvents are used, they are preferably employed in anamount up to about eight times the weight of the polygalactomannan.Preferably, with the water-miscible solvents, an amount of from about 1to 3 times the weight of the polygalactomannan is used. Withwater-immiscible solvents, an amount of from about three to five timesthe weight of the polygalactomannan is preferably employed.

The halo fatty acid reactant is used in an amount sufficient to increasethe hydration rate of the hydroxyalkyl polygalactomannans. Preferably,the said reactant will be used in an amount of about 0.5 to 5.0 percentby weight based on the weight of the polygalactomannan. Amounts belowthis range and in the lower part of the range improve hydration ratesmoderately while amounts of the halo fatty acid reactant above about 5.0percent give no additional advantages and for cost reasons are,therefore, not preferred.

Since alkali degradation may cause a reduction in the products viscosityproducing character, it is optional polysaccharides. And it is believedthat these carbonyl EXAMPLES III AND V-IX AND COMPARATlVE EXAMPLES IIAND IV Example I was essentially repeated with varying amounts of sodiumchloroacetate and/or with the addis v are Sites for any alkaliflegfadatiw e tion of sodium borohydride in Examples in and V-IX.pelygelaetemannan 8 The Sodmm borohydnde Example I was essentiallyrepeated without using sodithus optleneny added an amouflt of to P umchloroacetate (Example II) and without sodium cent y welght based on theweight of the pelygalae' chloroacetate but with sodium borohydride(Example tomannan- 10 IV). The products of all the Examples were thensub- At the eempleuon of the reaction, 1! Preferred to jected to varioustests with the data being set forth in neutralize the reaction mixtureby the addition of an the following Table;

7 TABLE 7 7 wt. percent sodium Wt. 1% Hydration rates afterchloropercent viscosity Percentacetate NaBH4 1 min. 2 min. 5 min 60 min.filtered 2.0 2,350 27.5 44.4 51.0 51.0 as 2,300 18.0 28.8 43.2 52.2 00.5 .04 3. 500 24. 0 a7. 8 51.0 54. 0 02 .04 a, 400 14. 4 36. 6 51. 0 54.s 0 1.0 04 3, 050 32. 4 43. s 54.0 55.2 01 2. 0 04 3, 250 26. 0 45. 05a. 4 55. 2 s7 2. 9 04 2, 650 45. 0 52. 2 55. 2 52. a n3 4. 0 .04 2,65050.4 54.4 57 5 5T. 5 s7 5. 0 04 2, 750 51. o 54. 6 5s. 2 57. 0 55 nightat C. The values are centipoises as measured with a Brookfieldviscometer at 10 r.p.rn.

2 Hydration rates were measured by the following procedure: 2.4 g. driedproduct was added at once to 600 g. distilled water (80 F.) that wasstirred rapidly in a Waring blendor (The Variac was set between andvolts and the blender turned on the high speed setting) After 10 secondsin the Blender, the sol was poured into a 600 ml. beaker and theviscosity measured with a Model 35 Faun viscometer at 100 r.p.n1.Measurements were made at l. 2 and 5 minutes after which the solutionwas placed in an 80 F. water bath for 55 minutes and the viscosity againmeasured. Since the reading at 60 minutes represents substantiallycomplete viscosity development, the rapidity of the hydration can hedetemiined from such reading and the readings at 1, 2 and 5 minutes.

3 Four hundred grams of the hydration rate solutions of were filteredthrough a J cm No. 50 Whatman filter paper in a pressure filter operatedat 100 p.s.i. The percent filtered is the amount of clear filtrateobtained up to the time the filtrate slows to :1 (hip. \nlues above 85%are most desired.

acid such as acetic, hydrochloric, sulfuric, nitric, and

The above data show that the halo fatty acid reactant the like.Additionally, the product may be filtered and 35 appreciably increasesthe hydration rate of the hydroxdried.

The following examples illustrate certain preferred embodiments of theinvention without being limiting. The examples also include comparativeproducts prepared without modification with the halo fatty acidreactant.

EXAMPLE I yalkyl polygalactomannans and that between about 2.9 and 4.0percent is optimum. The data also show that sodium borohydride tends toprevent loss of viscosity in the improved products.

We claim:

1. A hydroxyalkyl ether of a polygalactomannan prepared by reacting apolygalactomannan with (l an alkylene oxide of three to eight carbonatoms and (2) a chloro fatty acid reactant selected from chloro fattyacids of two to four carbon atoms and the alkali metal salts thereof,said chloro fatty acid reactant being used in an amount of about 0.5 to5.0 percent by weight based on the weight of the polygalactomannan andthe reactions of the alkylene oxide and the chloro fatty acid reactantwith the polygalactomannan being carried out in the presence of analkaline catalyst.

2. The product of claim 1 wherein the polygalactomannan is guar gum, thealkylene oxide is propylene oxide, the alkaline catalyst is sodiumhydroxide and the chloro fatty acid reactant is sodium chloroacetate i ii

2. The product of claim 1 wherein the polygalactomannan is guar gum, thealkylene oxide is propylene oxide, the alkaline catalyst is sodiumhydroxide and the chloro fatty acid reactant is sodium chloroacetate.